Gordy,
At the risk of beating a dead
horse:
Bruce's diagrams are carefully drawn and are
100% correct but I think it might be worth pointing
out again that he has
reduced the examples to rod motion only. As such, they are
conceptual
only and not necessarily a depiction of the
real world.
If we get into a mind set that says if the
butt end of the rod moves through space we
must have
translation taking place then we may be
mistaken.
If we hold the wrist rigid and rotate the
lower arm and rod combination about the
elbow we will get
something that looks very similar to Bruce's
drawing depicting a mixture of translation
and rotation,
i.e. the rod will rotate and the butt
of the rod will move through space, but the
motion will be rotation
only.
I've taken the liberty of attaching a
modified version of Bruce's spreadsheet showing what I hope
are some clarifications regarding rotation
and a mixture of translation and rotation. Bruce
was very careful to show that the axis of
rotation (the point that the rod is rotating around) is
the very butt end of the rod. As you can see
there will be a subtle difference when the axis
of rotation is moved to the elbow and we take
away translation - the butt of the rod will move
in a circular path, not a straight path - but
the outside observer could think they are
seeing a
combination of rotation and translation when
no translation exists.
I came across a fairly good discussion of
translation vs rotation at the following web site:
I'm curious - I haven't heard a response from
you regarding my question of whether it is
possible to pick up 30 feet of fly line plus
leader using translation only. Did you get
my email?
I could make it more of a challenge and ask
whether it is possible to pick up 50 feet plus
leader using translation only...
Again - I fully agree translation and
rotation are not subjects for most students. I do find them
helpful when discussing the difference
between arc and stroke.
Thanks
Walter
----- Original Message -----
Sent: Wednesday, September 03, 2008
8:30 PM
Subject: Rotation / Translation /
my error
Walter & Group..........
Bruce Richards sent us a spread sheet graphically depicting
TRANSLATION, ROTATION, A MIXTURE OF THE TWO AND DRIFT WITH TRANSLATION
AND WITH ROTATION. I've included these as an XL Spreadsheet
attachment. Here is his message:
Good points by both Troy and Walter. Walter has keyed on complex
rotations
caused by wrist/elbow/shoulder motions. To me, that is
style. If we
concentrate on what the rod actually does things get
much simpler, and that
is how we need to define motions, in terms of
the rod... Below I've
attached a simple Excel sheet I use to help
people understand rotation and
translation... The last tab shows 3
kinds of drift.....
(See attached file:
Rotation-Translation.xls)
Bruce
Scientific Anglers/3M
4100
James Savage Rd.
Midland, MI 48642 USA
Tel:
989-496-1113
Fax: 989-496-3374
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Allow me correct an error I made in one of our previous
messages.
I stated that max loading of the rod coincided with max rod tip
velocity. I WAS INCORRECT
!
Max. rod tip velocity occurs at RSP (Rod Straight
Position). MAX ROD LOAD (MAX. ROD BEND) OCCURS ABOUT ONE TENTH OF
A SECOND BEFORE THIS AT NEGATIVE ACCELERATION (THE STOP).
Putting it in different words: The greatest bend in the
rod is when the rod is loaded the most. This happens at or close
to the STOP. Between the STOP and the Rod Straight Position,
the rod tip is moving fastest.
At RSP, the loop begins to form. This marks the end of the
casting stroke (as many of us look at it.)
RSP is the point at which the rod UNLOADS.
Gordy
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
From Troy Miller:
I like Dennis' overall approach, in attempt to speak a language
that students can understand. I almost NEVER use the word
translation with a student, unless it's a CCI candidate. I say
"move the hand from here to here" while demoing.
I could not disagree more with this
statement:
If there is rotation during
translation it’s not translation !
Why can you not have other things happening to the object while
it's moving spacially? Shoot, on an atomic level, the electrons
are doing their own thing at the same time the macro-object is
translating, right?
Regards -- TAM
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Troy...
Yes .... the atoms keep twirling and the subatomic particles at a
nano level are doing their dance whilst we circle our sun and the whole
solar system hurtles through space on to some sort of infinity
!!!!!!
Bruce Richards and I both felt the same way. Perhaps
Dennis was thinking of a different concept when he typed that.
I, now, interpret his statement to mean that if there is
rotation during translation, that it is not PURE
TRANSLATION. With that, I'd agree. His prior
statements support my contention.
I find that most casts have a combination of translation and
rotation.
I, also, agree with you and Dennis that the use of the terms,
TRANSLATION and ROTATION have no place in teaching early casters.
In fact, I don't use them except when coaching MCCI candidates or in
discussing casting mechanics with very advanced casters who are
interested in the details.
Gordy
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Speaking of infinity:
I'm reminded of a time we had Ogden Nash as a guest. We
challenged him to come up with a rhyme for each word we chose. He
was incredible at doing that. I came up with the word,
INFINITY. His answer:
Dogs have fleas and pups
have fleas
and fleas have fleas that
bite-em.
The smaller fleas have lesser
fleas
and so ad infinitum
!
Gordy